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Grazia Paola Nicchia

Bio: Grazia Paola Nicchia is an academic researcher from University of Bari. The author has contributed to research in topics: Aquaporin 4 & Water transport. The author has an hindex of 35, co-authored 77 publications receiving 3414 citations. Previous affiliations of Grazia Paola Nicchia include Albert Einstein College of Medicine.


Papers
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Journal ArticleDOI
TL;DR: The purpose of this work is to integrate previous and recent data regarding AQP4 expression during BBB formation and depending on BBB integrity, using several experimental models.

194 citations

Journal ArticleDOI
TL;DR: Evidence is provided that dystrophin deficiency in mdx mice leads to disturbances in AQP4 assembly in the plasma membrane of fast skeletal muscle fibers and brain astrocytic end‐feet, suggesting that changes in the osmotic equilibrium of the neuromuscular apparatus may be involved in the pathology of muscular dystrophy.
Abstract: We report a detailed study of AQP4 expression in the neuromuscular system of mdx mice. Immunocytochemical analysis performed by double immunostaining revealed that mdx mice manifest a progressive reduction in AQP4 at the sarcolemmal level of skeletal muscle fast fibers and that type IIB fibers are the first to manifest this reduction in AQP4 expression. No labeling was observed in the cytoplasm of muscle fibers, indicating that the reduction in sarcolemma staining is not associated with an intracellular compartmentalization of mistargeted protein. By Western blot and RT-PCR analysis, we found that whereas the total content of AQP4 protein decreased (by 90% in adult mdx mice), mRNA levels for AQP4 remained unchanged. A similar age-related reduction in AQP4 expression was found in brain astrocytic end-feet surrounding capillaries of mdx mice. Morphometric analysis performed after immunogold electron microscopy indicated a reduction of approximately 85% in gold particles (32+/-2/microm vs. 4.7+/-0.61/microm). Western blot experiments conducted using membrane fractions from brain cortex revealed a strong reduction (of 70%) in AQP4 protein in adult mdx mice, and RT-PCR experiments demonstrated that the reduction was not at transcription level. More interesting was the finding that AQP4 reduction was associated with swelling of astrocytic perivascular processes whose ultrastructural modifications are commonly indicated as an important and early event in the development of brain edema. No apparent reduction in AQP4 was found in mdx stomach and kidney. Our data provide evidence that dystrophin deficiency in mdx mice leads to disturbances in AQP4 assembly in the plasma membrane of fast skeletal muscle fibers and brain astrocytic end-feet, suggesting that changes in the osmotic equilibrium of the neuromuscular apparatus may be involved in the pathology of muscular dystrophy.

188 citations

Journal ArticleDOI
TL;DR: Evidence is provided for the first time evidence for the expression of an aquaporin in skeletal muscle correlated to a specific fiber-type metabolism and a marked reduction of AQP4 expression suggesting a critical role in the membrane alteration of Duchenne muscular dystrophy.
Abstract: In this study we analyzed the expression of aquaporin-4 (AQP4) in mammalian skeletal muscle. Immunohistochemical experiments revealed that affinity-purified AQP4 antibodies stained selectively the sarcolemma of fast-twitch fibers. By immunogold electron microscopy, little or no intracellular labeling was detected. Western blot analysis showed the presence of two immunopositive bands with apparent molecular masses of 30 and 32 kD specifically present in membrane fraction of a fast-twitch rat skeletal muscle (extensor digitorum longus, EDL) and not revealed in a slow-twitch muscle (soleus). PCR Southern blot experiments resulted in a selective amplification in EDL of a 960-bp cDNA fragment encoding for the full-length rat form of AQP4. Functional experiments carried out on isolated skeletal muscle bundle fibers demonstrated that the osmotic response is faster in EDL than in soleus fibers isolated from the same rat. These results provide for the first time evidence for the expression of an aquaporin in skeletal muscle correlated to a specific fiber-type metabolism. Furthermore, we have analyzed AQP4 expression in skeletal muscle of mdx mice in which a decreased density of orthogonal arrays of particles, a typical morphological feature of AQP4, has been reported. Immunofluorescence experiments showed a marked reduction of AQP4 expression suggesting a critical role in the membrane alteration of Duchenne muscular dystrophy.

183 citations

Journal ArticleDOI
01 May 2003-Glia
TL;DR: The findings indicate that dystrophin deficiency in the mdx brain leads to severe injury of the endothelial and glial cells with disturbance in α‐actin cytoskeleton, ZO‐1, claudin‐ 1, and AQP4 assembly, as well as BBB breakdown.
Abstract: In this study, we investigated the involvement of the blood-brain barrier (BBB) in the brain of the dystrophin-deficient mdx mouse, an experimental model of Duchenne muscular dystrophy (DMD). To this purpose, we used two tight junction markers, the Zonula occludens (ZO-1) and claudin-1 proteins, and a glial marker, the aquaporin-4 (AQP4) protein, whose expression is correlated with BBB differentiation and integrity. Results showed that most of the brain microvessels in mdx mice were lined by altered endothelial cells that showed open tight junctions and were surrounded by swollen glial processes. Moreover, 18% of the perivascular glial endfeet contained electron-dense cellular debris and were enveloped by degenerating microvessels. Western blot showed a 60% reduction in the ZO-1 protein content in mdx mice and a similar reduction in AQP4 content compared with the control brain. ZO-1 immunocytochemistry and claudin-1 immunofluorescence in mdx mice revealed a diffuse staining of microvessels as compared with the control ones, which displayed a banded staining pattern. ZO-1 immunogold electron microscopy showed unlabeled tight junctions and the presence of gold particles scattered in the endothelial cytoplasm in the mdx mice, whereas ZO-1 gold particles were exclusively located at the endothelial tight junctions in the controls. Dual immunofluorescence staining of α-actin and ZO-1 revealed colocalization of these proteins. As in ZO-1 staining, the pattern of immunolabeling with anti–α-actin antibody was diffuse in the mdx vessels and pointed or banded in the controls. α-actin immunogold electron microscopy showed gold particles in the cytoplasms of endothelial cells and pericytes in the mdx mice, whereas α-actin gold particles were revealed on the endothelial tight junctions and the cytoskeletal microfilaments of pericytes in the controls. Perivascular glial processes of the mdx mice appeared faintly stained by anti-AQP4 antibody, while in the controls a strong AQP4 labeling of glial processes was detected at light and electron microscope level. The vascular permeability of the mdx brain microvessels was investigated by means of the horseradish peroxidase (HRP). After HRP injection, extensive perivascular areas of marker escape were observed in mdx mice, whereas HRP was exclusively intravascularly localized in the controls. Inflammatory cells, CD4-, CD8-, CD20-, and CD68-positive cells, were not revealed in the perivascular stroma of the mdx brain. These findings indicate that dystrophin deficiency in the mdx brain leads to severe injury of the endothelial and glial cells with disturbance in α-actin cytoskeleton, ZO-1, claudin-1, and AQP4 assembly, as well as BBB breakdown. The BBB alterations suggest that changes in vascular permeability are involved in the pathogenesis of the neurological dysfunction associated with DMD. GLIA 42:235–251, 2003. © 2003 Wiley-Liss, Inc.

168 citations

Journal ArticleDOI
TL;DR: Aquaporin‐4 KD in human astrocytes resulted in a morphological phenotype similar to that found in rat, and the strong down‐regulation of connexin43 (Cx43) with a concomitant reduction in cell coupling while no major alterations in Cx43 expression were found inRat and human cells demonstrate a primary role of this water channel in the cytoskeleton changes observed.
Abstract: Aquaporin-4 (AQP4), the main water channel in the brain, is expressed in the perivascular membranes of mouse, rat, and human astrocytes. In a previous study, we used small interfering RNA (siRNA) to specifically knock down AQP4 in rat astrocyte primary cultures and found that together with reduced osmotic permeability, AQP4 knockdown (KD) led to altered cell morphology. However, a recent report on primary cultured astrocytes from AQP4 null mice (KO) showed no morphological differences compared with wild types. In this study, we compared the effect of AQP4 KD in mouse, rat, and human astrocyte primary cultures and found that AQP4 KD in human astrocytes resulted in a morphological phenotype similar to that found in rat. In contrast, AQP4 KD in mouse astrocytes caused only very mild morphological changes. The actin cytoskeleton of untreated astrocytes exhibited strong species-specific differences, with F-actin being organized in cortical bands in mouse and in stress fibers in rat and human astrocytes. Surprisingly, as a consequence of AQP4 KD, F-actin cytoskeleton was depolymerized in rat and human whereas it was completely rearranged in mouse astrocytes. Although AQP4 KD induced alterations of the cell cytoskeleton, we found that the expression of dystrophin (DP71), beta-dystroglycan, and alpha-syntrophin was not altered. AQP4 KD in cultured mouse astrocytes produced strong down-regulation of connexin43 (Cx43) with a concomitant reduction in cell coupling while no major alterations in Cx43 expression were found in rat and human cells. Taken together, these results demonstrate that with regard to these properties, human astrocytes in culture are more similar to rat than to mouse astrocytes. Moreover, even though AQP4 KD in mouse astrocytes did not result in a dramatic morphological phenotype, it induced a remarkable rearrangement of F-actin, not related to disruption of the dystrophin complex, indicating a primary role of this water channel in the cytoskeleton changes observed. Finally, the strong down-regulation of Cx43 and cell coupling in AQP4 KD mouse astrocytes indicate that a functional relationship likely exists between water channels and gap junctions in brain astrocytes.

154 citations


Cited by
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Journal ArticleDOI
TL;DR: An anatomically distinct clearing system in the brain that serves a lymphatic-like function is described and may have relevance for understanding or treating neurodegenerative diseases that involve the mis-accumulation of soluble proteins, such as amyloid β in Alzheimer's disease.
Abstract: Because it lacks a lymphatic circulation, the brain must clear extracellular proteins by an alternative mechanism. The cerebrospinal fluid (CSF) functions as a sink for brain extracellular solutes, but it is not clear how solutes from the brain interstitium move from the parenchyma to the CSF. We demonstrate that a substantial portion of subarachnoid CSF cycles through the brain interstitial space. On the basis of in vivo two-photon imaging of small fluorescent tracers, we showed that CSF enters the parenchyma along paravascular spaces that surround penetrating arteries and that brain interstitial fluid is cleared along paravenous drainage pathways. Animals lacking the water channel aquaporin-4 (AQP4) in astrocytes exhibit slowed CSF influx through this system and a ~70% reduction in interstitial solute clearance, suggesting that the bulk fluid flow between these anatomical influx and efflux routes is supported by astrocytic water transport. Fluorescent-tagged amyloid β, a peptide thought to be pathogenic in Alzheimer's disease, was transported along this route, and deletion of the Aqp4 gene suppressed the clearance of soluble amyloid β, suggesting that this pathway may remove amyloid β from the central nervous system. Clearance through paravenous flow may also regulate extracellular levels of proteins involved with neurodegenerative conditions, its impairment perhaps contributing to the mis-accumulation of soluble proteins.

3,368 citations

Journal ArticleDOI
24 Jan 2008-Neuron
TL;DR: These findings support developments of new therapeutic approaches for chronic neurodegenerative disorders directed at the blood-brain barrier and other nonneuronal cells of the neurovascular unit.

2,797 citations

Journal ArticleDOI
TL;DR: Mammalian skeletal muscle comprises different fiber types, whose identity is first established during embryonic development by intrinsic myogenic control mechanisms and is later modulated by neural and hormonal factors.
Abstract: Mammalian skeletal muscle comprises different fiber types, whose identity is first established during embryonic development by intrinsic myogenic control mechanisms and is later modulated by neural and hormonal factors. The relative proportion of the different fiber types varies strikingly between species, and in humans shows significant variability between individuals. Myosin heavy chain isoforms, whose complete inventory and expression pattern are now available, provide a useful marker for fiber types, both for the four major forms present in trunk and limb muscles and the minor forms present in head and neck muscles. However, muscle fiber diversity involves all functional muscle cell compartments, including membrane excitation, excitation-contraction coupling, contractile machinery, cytoskeleton scaffold, and energy supply systems. Variations within each compartment are limited by the need of matching fiber type properties between different compartments. Nerve activity is a major control mechanism of the fiber type profile, and multiple signaling pathways are implicated in activity-dependent changes of muscle fibers. The characterization of these pathways is raising increasing interest in clinical medicine, given the potentially beneficial effects of muscle fiber type switching in the prevention and treatment of metabolic diseases.

2,107 citations

Journal ArticleDOI
TL;DR: It is shown that NMO-IgG binds selectively to the aquaporin-4 water channel, a component of the dystroglycan protein complex located in astrocytic foot processes at the blood-brain barrier, which may represent the first example of a novel class of autoimmune channelopathy.
Abstract: Neuromyelitis optica (NMO) is an inflammatory demyelinating disease that selectively affects optic nerves and spinal cord. It is considered a severe variant of multiple sclerosis (MS), and frequently is misdiagnosed as MS, but prognosis and optimal treatments differ. A serum immunoglobulin G autoantibody (NMO-IgG) serves as a specific marker for NMO. Here we show that NMO-IgG binds selectively to the aquaporin-4 water channel, a component of the dystroglycan protein complex located in astrocytic foot processes at the blood-brain barrier. NMO may represent the first example of a novel class of autoimmune channelopathy.

2,024 citations

Journal ArticleDOI
TL;DR: The pathogenesis of increased BBB permeability in hypoxia-ischemia and inflammatory mechanisms involving the BBB in septic encephalopathy, HIV-induced dementia, multiple sclerosis, and Alzheimer disease are described.

2,014 citations